290 102 



sible, that he really has obsened the male, but besides it must be emphasised that 

 some main points in the structure have been overlooked or uncorrectly interpreted. 

 This especially holds good \Yith regard to the proboscis-like projection, within the 

 ciliary wreath. Wesché further indicates one single eye. It is highly remarkable, 

 that he has further found dorsal and lateral antennæ, excretory canals and even a 

 large contractile vesicle and a foot well separated from the body; neither Plate nor 

 myself have in any of the males belonging to this genus been able to see anything 

 of this kind. The contractile vesicle indicated by Wesché in his text is not found 

 in his figures. 



In the sexual periods the males occur in great numbers and may then be caught 

 in the lighted borders of the vessel. 



Triarthra mystacina Ehrbg. 

 Tab. XV, flg, 2. 

 Description. The male resembles that of T. longisefa very much. The pro- 

 boscis-like projection is much shorter; I have been unable to find any organs but 

 the very large testis and the two red eyes; no prostata glands: the penis is shaped 

 as in T. longiseta but no sensitive hairs have been found. Size of male 70 //, of female 

 200 /;. T. mijstacina is extremely common in smaller ponds. During the two maxima 

 April — May and Sept. — Oct. the males occur in great numbers. 



Triarthra breviseta Gosse. 

 = T. cornuta Weisse. 



Male: Plate 1886, p. 21. 

 Tab. XV, flg. 3. 



Plate describes the male as follows. 



"Die Männchen haben ungefähr eine Grösse von n,08 und in der Gestalt viel .\linlichkeit 

 mit den Männchen der noch zu bescreibenden Hertwigia volvocicola. Sie sind cylindrisch, be- 

 sitzen vorn einen Cilienkranz, über den die Cuticula, ohne weiter bewimpert zu sein, halbkuge- 

 lich vorspringt. In den daselbst gelegenen Matrixverdickungen, vielleiclit auch in Verbindung 

 mit dem grossen Gehirn, sitzen zwei rote Augen flecke, die wie bei den Weibchen deutliche 

 lichtbrechende Körperchen erkennen lassen. Nach hinten verjüngt sich das Tier, und da der 

 enge, flimmernde .\usfulirgang des Hodens am aboralen Körperende ausmündet, dient dieses 

 zugleich als Penis. Gehirn und rudimentärer Darm bieten nichts Bemerkenswertlies. Tastiiüchel, 

 Wassergefässe und contractile Blase habe ich bei der steten Bewegliclikeit des Tierchens ver- 

 gebens gesucht." 



Description. The male resembles those of the just described tw'o species very 

 much, but the proboscis-like projection is very short, often rising only a little above 

 the ciliary wreath. Of inner organs I have only been able to observe the brain and 

 the very large testis. The penis is very short; the peculiar chitin staffs in the two 

 other species I have not found here. Size of male 60,«, of female 120,(/. 



As mentioned above Plate has seen the male, but gives no figure; his description 

 and mine agree fairlj- well. 



